Steam autoclaving is the hospital standard for sterilizing most medical instruments. This method exposes materials to steam at 121° C. at 15-20 lbs of pressure for 15-30 minutes. Killing is mediated by heat denaturation of proteins, DNA, and subsequent interruption of metabolic functions. The method requires cumbersome equipment, a power supply and plumbing, although benchtop models have fillable water tables. Aside from these logistical problems, autoclaving is not suitable for many plastics and other heat labile materials.
Sterilant gases can kill or control the growth of microbial contaminations. Some of these sterilant gases include chlorine dioxide, sulfur dioxide, hydrogen peroxide, nitric oxide, nitrogen dioxide, carbon dioxide, hydrogen sulfide, ozone and ethylene oxide. One problem with many of the sterilant gases is that they are explosive in high concentrations (e.g. ethylene oxide, hydrogen peroxide, chlorine dioxide, ozone). Thus, storing, containing and using these gases in high concentrations represent a hazard to the user. For safety reasons, this limits the usable concentration of gas and creates an additional disadvantage. That is because the concentration of the sterilant gas must be decreased due to safety concerns, the exposure time must be increased to achieve effective sterilization. In general, therefore, the more hazardous the chemical in terms of its potential as a chemical hazard, the longer the sterilization cycle becomes.
Certain sterilant gases, such as chlorine dioxide, ozone and hydrogen peroxide are difficult and expensive to transport. Many of these sterilant gases are powerful oxidizers. Oxidizing gases are expensive and paperwork intensive to ship in bulk tanks, further complicating their use. Gases, such as ozone and chlorine dioxide, must be generated at or near the point of use. On-site plants for generating one such sterilant gas, chlorine dioxide, are costly and require significant space to implement.
Hamilton U.S. Pat. No. 6,607,696 describes device for delivering chlorine dioxide to disinfect or sterilize a liquid or an item contained in the liquid. The device uses a permeable sachet containing gas generating reactants, such as sodium chlorite and citric acid, where the sachet is a receptacle permeable to liquid and gas. Liquid can diffuse into the receptacle to reach the gas generating reactants that then generate a gas, such as chlorine dioxide. The gas that diffuses out of the permeable sachet is not sealed from the environment/atmosphere. Multi-compartmental devices that employ gas-generating ingredients contained in closed compartments that are permeable and permit the diffusion of liquids and gases through the compartments to produce chlorine dioxide, such as the sachet and envelope compartments used in U.S. Pat. Nos. 6,602,466 and 6,607,696. Not only are these systems expensive and difficult to manufacture, but they do not contain the generated gases in a manner that prevents their unintended escape to the environment/atmosphere nor do they allow the user to predictably and controllably release the gas into a sealable container that is sealed when the contents are sterilized.
Thus, there is a need for methods and devices that generate sterilant gases at the point of use in a safe, and efficient manner. There is a further need for processes capable of producing significant concentrations of sterilant gas without the danger of explosion or oxidative fire. There is a need to produce greater concentrations of NO in a short time period to allow a shorter exposure and make the sterilization process more efficient. There is also a need for a system and method to generate small amounts of sterilant gas in an economical manner. The ability to economically generate small amounts of sterilant gases allows for easy transportation of the sterilizing system, imparting a portability to the system not commonly found with traditional sterilization devices and methods.
Thus, given the problems with traditional gaseous sterilants and disinfectants, there is a need for a sterilant gas generating system and method where the risk of explosion and oxidative fire is minimized, that produces the sterilant gas rapidly, safely, economically, and in a scaleable manner. In addition, there is a need for a gas that can be safely used at high enough concentrations to act rapidly to minimize the time required for sterilization or disinfecting.